Sheet aligning mechanisms in image forming devices use a variety of methods for registering sheets in process (forward), lateral (side-to-side), and skew (rotation) directions. Precise registration is important for reliable and accurate image production and/or reproduction.
Sheet handling and registration systems today can perform all three registration functions nearly simultaneously and with sheets moving along a paper path at a controlled speed, without sheet stoppages. This is otherwise known as in-process sheet registration, or more colloquially, sheet registration “on the fly.” The requirement advantageously to conduct sheet printing operations at ever increasing speeds challenges conventional sheet handling and registration systems. An ability to achieve a desired sheet skew rotation, sheet lateral movement, and forward sheet speed adjustment during ever briefer time periods presents unique challenges in various systems.
Conventional systems use two high-power servo-motors or step motors for driving a laterally spaced pair of separate sheet driving nips. Motors mounted on transversely-movable carriage assemblies with respect to the feed path to achieve both skew and lateral adjustment add significant proportional weight to the carriage. This additional weight makes it difficult to control rapid movement as may be required for lateral adjustment.